Parking garage environment detection and ehpe determination for vehicular navigation

ABSTRACT

Implementations of the present invention contemplate obtaining a more accurate estimated horizontal position error (EHPE) under conditions in which the telematics unit of a vehicle cannot receive GNSS signals. In particular, the invention contemplates determining that a vehicle is entering a parking garage and obtaining a more accurate estimated horizontal position error (EHPE) of the vehicle in the parking garage when GNSS signals are unavailable.

TECHNOLOGY FIELD

The present disclosure relates generally to vehicular telematics systemsand more specifically to the use of a telematics unit within a vehiclefor navigation within covered structures such as parking garages.

BACKGROUND

Telematics units within mobile vehicles provide subscribers withconnectivity to a telematics service provider (TSP). The TSP providessubscribers with an array of services ranging from emergency callhandling and stolen vehicle recovery to diagnostics monitoring, globalnavigation system aided position identification, map services, andturn-by-turn navigation assistance. Telematics units are oftenprovisioned and activated at a point of sale when a subscriber purchasesa telematics-equipped vehicle. Once provisioned and activate, telematicsunits can be utilized by a subscriber to obtain telematics services,such as those described herein, from the TSP.

One service provided by a TSP is a Global Navigation Satellite System(GNSS) based navigation service. GNSS is a generic term referring to anyof multiple satellite constellation-based global positioning networksincluding, for example, the. Global Positioning System (GPS)constellation. Another GNSS constellation network is the GlobalNavigation Satellite System (GLONASS). A particular example of a GNSSbased navigation service is the provision of turn-by-turn (TBT)directions from a current location of a vehicle or an alternative startlocation to a specified destination.

However, under certain conditions, GNSS signals received by thetelematics unit in a vehicle are too weak to provide meaningfullyaccurate information regarding the position of the vehicle. For example,the telematics unit in a vehicle traveling in a parking garage, tunnel,or other underground or covered structure may be unable to receive GNSSsignals. Under such conditions, the driver of the vehicle is unable torely on the GNSS navigation services provided by the TSP. In order toprovide navigation services under conditions where GNSS signals are tooweak, the telematics unit must rely on a Dead Reckoning (DR) system.However, DR systems are not able to provide position information withthe level of accuracy provided by a GNSS.

SUMMARY OF THE INVENTION

Implementations of the present invention contemplate obtaining a moreaccurate estimated horizontal position error (EHPE) under conditions inwhich the telematics unit of a vehicle cannot receive GNSS signals. Inparticular, the invention contemplates determining that a vehicle isentering a parking garage and obtaining a more accurate estimatedhorizontal position error (EHPE) of the vehicle in the parking garagewhen GNSS signals are unavailable.

One implementation consists of a method, implemented at a telematicsunit of a vehicle, for calculating the estimated horizontal positionerror (EHPE) of a position of a vehicle provided by a dead reckoning(DR) system, the method comprising determining that the vehicle isoperating within a parking garage, wherein determining that the vehicleis operating within a parking garage triggers the use of a parkinggarage mode by a DR system of the telematics unit, and determining theEHPE of the vehicle according to the parking garage mode of the DRsystem.

An additional implementation consists of a computer readable mediumhaving stored thereon a set of computer executable instructions forcalculating the estimated horizontal position error (EHPE) of a positionof a vehicle provided by a dead reckoning (DR) system, the set ofinstructions comprising instructions for determining that the vehicle isoperating within a parking garage, wherein determining that the vehicleis operating within a parking garage triggers the use of a parkinggarage mode by a DR system of the telematics unit, and determining theEHPE of the vehicle according to the parking garage mode of the DRsystem.

A further implementation consists of a telematics unit configured toreceive GNSS signals and to determine the position of a vehicle throughdead reckoning (DR) techniques when it is unable to receive GNSSsignals, the telematics unit comprising a processor configured todetermine that the vehicle is operating within a parking garage andfurther configured to execute a parking garage DR mode upon determiningthat the vehicle is operating within the parking garage wherein theparking garage DR mode determines an estimated horizontal position error(EHPE) of the position of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

While the appended claims set forth the features of the presentinvention with particularity, the invention, together with its objectsand advantages, may be best understood from the following detaileddescription taken in conjunction with the accompanying drawings ofwhich:

FIG. 1 is a schematic diagram of an operating environment for a mobilevehicle communication system, which includes a call center of atelematics service provider, usable in implementations of the describedprinciples;

FIG. 2 is a flow chart summarizing an example process executed by atelematics unit of a vehicle for determining the estimated horizontalposition error (EHPE) of a position of a vehicle provided by a deadreckoning (DR) system;

FIG. 3 is a flow chart summarizing an example process executed by atelematics service provider for determining whether a vehicle iscurrently operating in a parking structure or that operation of thevehicle within a parking structure is imminent;

FIG. 4 is a graphical representation depicting the EHPE as determined bya variety of techniques.

DETAILED DESCRIPTION OF THE DRAWINGS

Before discussing the details of the invention, a brief overview of anexample telematics system is given to guide the reader. FIG. 1schematically depicts an example environment for carrying out theinvention. It will be appreciated that the described environment is anexample, and does not imply any limitation regarding the use of otherenvironments to practice the invention. With reference to FIG. 1 thereis shown an example of a communication system 100 that may be used withthe present systems and methods and generally includes a vehicle 102, awireless carrier system 104, a land network 106 and a call center 108 ofa telematics service provider (TSP). It should be appreciated that theoverall architecture, setup and operation, as well as the individualcomponents of a system such as that shown in FIG. 1 are generally knownin the art. Thus, the following paragraphs provide a brief overview ofone such example information system 100. However, present systems andmethods could be carried out in other environments as well.

Vehicle 102 is a mobile vehicle such as a motorcycle, car, truck,recreational vehicle (RV), etc., and is equipped with suitable hardwareand software that enables it to communicate over system 100.Additionally, vehicle hardware 110 shown generally in FIG. 1 includes: atelematics unit 114, a microphone 116, a speaker 118, and buttons and/orcontrols 120 connected to the telematics unit 114. A network connectionor vehicle bus 122 is operatively coupled to the telematics unit 114.Examples of suitable network connections include a controller areanetwork (CAN), a media oriented system transfer (MOST), a localinterconnection network (LIN), an Ethernet, and other appropriateconnections such as those that conform with known ISO, SAE, and IEEEstandards and specifications, to name but a few.

The telematics unit 114 is an onboard device providing a variety ofservices through its communication with the call center 108, andgenerally includes an electronic processing device 128, one or moretypes of electronic memory 130, a cellular chipset/component 124, awireless modem 126, a dual antenna 129 and a navigation unit containinga GNSS chipset/component 132. The GNSS chipset/component may be, e.g., aGPS chipset/component. The GNSS chipset/component is capable ofdetermining the location of the vehicle with a high degree of accuracy.For example, the GNSS chipset, component could determine that anelectric vehicle is located at a particular electric vehicle chargingstation. In one example, the wireless modem 126 comprises, and iscarried out in the form of, a computer program and/or set of softwareroutines executing within the electronic processing device 128. Thecellular chipset/component 124 and the wireless modem 126 may he calledthe network access device (NAD) of the telematics unit 114. The NAD 114further includes a short-range wireless unit 131 capable ofcommunicating with a user's mobile device such as a cellular phone,tablet computer, PDA, or the like, over a short-range wireless protocol.For example, in one implementation, the short-range wireless unit 131 isa Bluetooth unit with an RF transceiver that communicates with a user'smobile device using Bluetooth protocol.

The telematics unit 114 provides a variety of services for subscribers.Examples of such services include: turn-by-turn directions and othernavigation-related services provided in conjunction with the GNSS basedchipset/component 132; airbag deployment notification and otheremergency or roadside assistance-related services provided in connectionwith various crash and or collision sensor interface modules 133 andsensors 135 located throughout the vehicle.

GNSS navigation services are implemented based on the geographicposition information of the vehicle provided by the GNSS basedchipset/component 132. A user of the telematics unit enters adestination using inputs corresponding to the GNSS component, and aroute to a destination is calculated based on the destination addressand a current position of the vehicle determined at approximately thetime of route calculation. Turn-by-turn (TBT) directions may further heprovided on a display screen corresponding to the GNSS component and/orthrough vocal directions provided through a vehicle audio component 137.It will be appreciated that the calculation-related processing may occurat the telematics unit or may occur at a call center 108. Furthermore,the telematics unit 114 may be configured to determine, based uponinformation provided by the GNSS based chipset/component 132, that thevehicle 102 is entering or is about to enter a parking structure. Insome implementations, the GNSS based chipset/component 132 itself isconfigured to determine that the vehicle 102 is about to enter a parkinggarage. For example, the GNSS based chipset/component 132 may executesoftware that includes the locations of all known parking structures andthat issues a notification when the vehicle travels into one of theknown multi-level parking garages.

The telematics unit 114 further includes a dead reckoning engine 127which is a component of the electronic processing device 128. The deadreckoning engine 127 is a processor that is configured to determine anestimated horizontal position error (EHPE) of the position of thevehicle. The dead reckoning engine may calculate the EHPE under avariety of circumstances and may utilize a variety of techniques tocalculate the EHPE depending on the circumstance. For example, The deadreckoning engine 127 of the telematics unit 114 may utilize onetechnique to calculate the EHPE when the GNSS chipset/component 132 isreceiving signals from a GNSS satellite and may utilize a differenttechnique to calculate the EHPE when the GNSS chipset/component 132 isnot receiving a signal from a GNSS satellite or is receiving a signalthat is too weak to he utilized. The dead reckoning engine 127 may alsoutilize a different technique to calculate the EHPE when it isdetermined that the vehicle has entered a parking structure.

Infotainment-related services are provided by the TSP wherein music, Webpages, movies, television programs, video games and/or other content isdownloaded to an infotainment center 136 operatively connected to thetelematics unit 114 via a vehicle bus 122 and an audio bus 112. In oneexample, downloaded content is stored for current or later playback.

The preceding list of functions is by no means an exhaustive list of allof the capabilities of telematics unit 114, as should be appreciated bythose skilled in the art, but is simply an illustration of some of theservices that the telematics unit 114 offers. The telematics unit 114may include a number of components known by those skilled in the art isaddition to those described above.

Vehicle communications use radio transmissions to establish acommunications channel within the wireless carrier system. 104 so thatvoice and/or data transmissions occur over the n e communicationschannel. Vehicle communications are enabled via the cellularchipset/component 124 for voice communications and a wireless modem 126for data transmission. For example, data pertaining to a forecast of autility's renewable energy mixture can be transmitted to the telematicsunit 114 via the wireless modem 126.

To enable successful data transmission over the communications channel,wireless modem 126 applies some form of encoding or modulation toconvert the digital data so that it can communicate through a vocoder orspeech codec incorporated in the cellular chipset/component 124. Anysuitable encoding or modulation technique that provides an acceptabledata rate and bit error can be used with the present method. The dualmode antenna 129 services the GLASS chipset/component and the cellularchipset/component.

The microphone 116 provides the driver or other vehicle occupant with ameans for inputting verbal or other auditory commands, and can beequipped with an embedded voice processing unit utilizing ahuman/machine interface (HMI) technology known in the art. Conversely,the speaker 118 provides verbal output to the vehicle occupants and canhe either a stand-alone speaker specifically dedicated for use with thetelematics unit 114 or can be part of the vehicle audio component 137.In either event, the microphone 116 and the speaker 118 enable vehiclehardware 110 and the call center 108 to communicate with the occupantsthrough audible speech.

The vehicle hardware also includes the one or more buttons or controls120 configured to enable a vehicle occupant to activate or engage one ormore of the vehicle hardware components 110. For example, one of thebuttons 120 is an electronic push button that, when pressed, initiatesvoice communication with the call center 108 (whether it be a liveadvisor 148 or an automated call response system). In another example,one of the buttons 120, when pushed, initiates emergency services.

The audio component 137 is operatively connected to the vehicle bus 122and the audio bus 112. The audio component 137 receives analoginformation, rendering it as sound, via the audio bus 112. Digitalinformation is received via the vehicle bus 122. The audio component 137provides AM and FM radio, CD, DVD, and multimedia functionalityindependent of the infotainment center 136. The audio component 137contains a speaker system, or alternatively utilizes the speaker 118 viaarbitration on the vehicle bus 122 and/or the audio bus 112.

The vehicle crash and/or collision detection sensor interface 133 isoperatively connected to the vehicle bus 122. The crash sensors 135provide information to the telematics unit 114 via the crash and/orcollision detection sensor interface 133 regarding the severity of avehicle collision, such as the angle of impact and the amount of forcesustained. Vehicle sensors 139, connected to various sensor interfacemodules 134 are operatively connected to the vehicle bus 122. Thevehicle sensors 139 can also include but are not limited to gyroscopes,accelerometers, magnetometers, emission detection and/or controlsensors, and the like. The sensor interface modules 134 can includepower train control, climate control, and body control, to name but afew.

The wireless carrier system 104 can be a cellular telephone system orany other suitable wireless system that transmits signals between thevehicle hardware 110 and the land network 106. According to an example,the wireless carrier system 104 includes one or more cell towers 138,base stations and/or mobile switching centers (MSCs) 140, as well as anyother networking components required to connect the wireless system 104with the land network 106. The mobile switching center may include aremote data server.

As appreciated by those skilled in the art, various cell tower/basestation/MSC arrangements are possible and could be used with thewireless system 104 (also referred to as the “cellular network” herein).For example, a base station and a cell tower could be co-located at thesame site or they could be remotely located, a single base station couldbe coupled to various cell towers, and various base stations could becoupled with a single MSC, to name but a few of the possiblearrangements. Preferably, a speech codec or vocoder is incorporated inone or more of the base stations, but depending on the particulararchitecture of the wireless network, it could be incorporated within aMobile Switching Center or sonic other network component as well.

The land network 106 is, for example, a conventional land-basedtelecommunications network connected to one or more landline telephonesand connecting wireless carrier network 104 to call center 108. Forexample, the land network 106 includes a public switched telephonenetwork (PSTN) and/or an Internet protocol (IP) network, as isappreciated by those skilled in the art. Of course, one or more segmentsof the land network 106 are implemented in the form of a standard wirednetwork, a fiber or other optical network, a cable network, otherwireless networks such as wireless local networks (WLANs) or networksproviding broadband wireless access (BWA) or any combination thereof.

The call Center (OCC) 108 of the telematics service provider is designedto provide the vehicle hardware 110 with a number of different systemback-end functions and, according to the example shown here, generallyincludes one or more switches 142, servers 144, databases 146, liveadvisors 148, and a variety of other telecommunication and computerequipment 150 that is known to those skilled in the art. These variouscall center components are coupled to one another, for example, via anetwork connection or bus 152, such as the one previously described inconnection with the vehicle hardware 110. Switch 142, which can be aprivate branch exchange (PBX) switch, roues incoming signals so thatvoice transmissions are usually sent to either the live advisor 148 oran automated response system, and data transmissions are passed on to amodem or other piece of telecommunication and computer equipment 150 fordemodulation and further signal processing.

The telecommunication and computer equipment 150 includes a modem thatpreferably includes an encoder, as previously explained, and can beconnected to various devices such as application servers 144 anddatabases 146. For example, the databases 146 could be designed to storesubscriber profile records or any other pertinent subscriberinformation. Although the illustrated example has been described as itwould be used in conjunction with a manned call center, it will beappreciated that the call center 108 can be any central or remotefacility, manned or unmanned, mobile or fixed, to or from which it isdesirable to exchange voice and data The servers 144 interface withdatabases 146 and telematics units such as the telematics unit 114. Theservers 144 have processors that can be configured to request andreceive information from telematics units such as the telematics unit114. In some implementations, information requested and received by theservers 144 is subsequently stored in the databases 146.

In general terms, not intended to limit the claims, the exampleenvironment depicted by FIG. 1 may be used by systems and methods thatobtain a more accurate estimated horizontal position error (EHPE) underconditions in which the telematics unit of a vehicle cannot receive GNSSsignals. In particular, the invention contemplates determining that avehicle is entering a parking garage and obtaining a more accurateestimated horizontal position error (EHPE) of the vehicle in the parkinggarage when GNSS signals are unavailable by utilizing a particularmethod of determining HUE that accounts for conditions typical of aparking garage environment.

In situations where GNSS signals are weak or unavailable, vehicularnavigation systems rely on the use of dead reckoning (DR) systems tocalculate an estimate of the current geographical location of thevehicle. DR systems utilize a previously determined position of thevehicle and calculate the estimate of the position of the vehicle at alater point using a plurality of sensor readings. In order to calculatethe estimate of the position of the vehicle at a later point in time,the vehicle uses data provided by one or more vehicular sensors todetermine a track of the vehicle from the previously determinedposition. For example, the vehicle sensors can include a vehicle speedsensor, a steering wheel position sensor, and a gyroscope, and canprovide sensor data pertaining to, e.g., the vehicle's speed, the numberof rotations of the wheels of the vehicle, the heading of the vehicle,the orientation of the vehicle, and the steering wheel position of thevehicle. The vehicle may then utilize a Kalman filter to integrate thedata provided by the vehicular sensors with data provided by the GNSSsignals to calculate an estimated geographical location of the vehiclewhen the GNSS signals are weak or unavailable.

In calculating the position of a vehicle when GNSS signals are weak orunavailable, the DR system calculates an estimated horizontal positionerror (EHPE). Methods for calculating the RIPE are well known in theart. For example, the EHPE can be calculated with the predictioncovariance matrix of the Kalman filter. If the prediction covariancematrix of the Kalman filter at time k is P⁻(k), and the diagonalelements of P⁻(k) are (P₃ ⁻(k), P_(n) ⁻(k)) where P_(e) ⁻ is thelongitude prediction covariance in meters and P_(n) ⁻(k) is the latitudeprediction covariance in meters, then the EHPE at time k can becalculated according to the formula. EHPE(k)=√{square root over(P_(hu −)(k)+p_(n) ⁻(k))}{square root over (P_(hu −)(k)+p_(n) ⁻(k))}.FIG. 2, described herein below, is a flow chart summarizing an exampleprocess executed by a telematics unit of a vehicle for calculating theestimated horizontal position error (EHPE) of a geographical location ofa vehicle provided by a dead reckoning (DR) system. However, calculatingthe EHPE with the prediction covariance matrix of the Kalman filter isgenerally not accurate, and the calculated EHPE is frequently much lessthan the actual horizontal position error.

Additionally, the EHPE can be calculated by multiplying the estimatedheading error (EHE) of the vehicle at time k by the distance traveledduring a time interval beginning from a previous point in time at whichthe vehicle's EHPE was calculated. Specifically, the EHPE at time k canbe calculated according to the formula EHPE(k)=(EHPE(k−1)+hE(k)·Δd(k)where the EHE (in radians) of the vehicle at time k is hE(k), thedistance traveled from time k−1 to time k is Δd(k), and the EHPE at timeis k−1 is EHPE(k−1). The EHE of the vehicle at time k can be calculatedaccording to the equation hE(k)=hE(j)+σ_(b)(k−j)Δt+σ_(w)√{square rootover ((k−j)Δt)} where k>j,j is the initial time of propagation, hE(j) isthe EHE at time j, Δt is the interval between two time points, σ_(b) isthe standard deviation of the gyroscope constant drift, and σ^(w) is thestandard deviation of the gyroscope measurement noise. However,calculating the EHPE by multiplying the EHE by the distance traveleddoes not compensate for horizontal position error reductions resultingfrom 180 degree heading changes and therefore systematicallyoverestimates the horizontal position error in situations in which thevehicle's heading changes by 180 degrees.

In a parking garage environment, a vehicle's heading constantly changes,often by 180 degrees or more. Therefore, calculating the EHPE of thevehicle's position by multiplying the estimated heading error by thedistance traveled will not provide an accurate estimate of the actualhorizontal position error. Furthermore, calculating the EHPE of thevehicle according to the prediction covariance of the Kalman filter willalso not provide an accurate estimate of the actual horizontal positionerror. Systems and methods of the present disclosure enable a moreaccurate calculation of the EHPE to be made. The present disclosurecontemplates first determining that a vehicle is operating within aparking garage environment, or that operation of the vehicle within aparking garage environment is imminent. The present disclosure furthercontemplates triggering the execution of a parking garage dead reckoningmode for calculating the EHPE of the vehicle in response to detectingvehicle operation within a parking garage environment or detectingimminent operation within a parking garage.

FIG. 2 is a flow chart summarizing an example process executed by atelematics unit of a vehicle for calculating the estimated horizontalposition error (EHPE) of a position of a vehicle provided by a deadreckoning (DR) system. At step 200, the process determines that thevehicle 102 is either operating within a parking garage environment orthat operation of the vehicle 102 within a parking garage environment isimminent. Where operation within the parking garage is imminent, theprocess may estimate a time at which the vehicle will begin operating inthe parking garage. Such an estimate may arise from determining themeasured position of the vehicle, determining the position of theentrance to the parking garage, and calculating an estimated time atWhich the vehicle will enter the parking garage.

In an implementation, a determination that the vehicle 102 is or isabout to enter a parking garage environment is based on data acquiredfrom the GNSS chipset/component 132. More particularly, data acquiredfrom the GNSS chipset/component 132 is used to determine the location ofthe vehicle and the location information is compared to map informationto determine whether such location indicated by the GNSSchipset/component 132 corresponds to a parking garage location. Aparking garage location may be defined as a geographical area. Forexample, a parking garage location may be defined by a set of locationsthat define a perimeter of a geographical area Similarly, a parkinggarage location may be identified by a range of coordinates. Forexample, the vehicle location provided by the data acquired from theGNSS chipset/component 132 may be cross-referenced with a list oflocations corresponding to parking garages. The cross-referencing may beperformed by the telematics unit 114 of the vehicle 102, by othervehicle hardware components, by one of the servers 144 of the callcenter 108 of the TSP, or by other hardware elements of the TSP. In oneimplementation, the process summarized in FIG. 2 may determine that thevehicle is operating within a parking garage environment by analyzingheading change characteristics of vehicular movement. In such animplementation, analyzing heading change characteristics of vehicularmovement involves determining the value of S hd(k+L)−S_hd(k), whereinS_hd(k) is the heading change accumulation at time k, and S_hd(k+L) isthe heading change accumulation at time k+L. If (k+L)−S_hd (k)>180°, itmay be determined that the vehicle is operating in a parking garageenvironment.

In one implementation, determining that the vehicle is entering or isabout to enter a parking structure at step 200 involves a combination ofanalyzing data acquired from the GNSS chipset/component 132 andanalyzing heading change characteristics of the vehicular movement. Insuch an implementation, determining that the vehicle is or is about tobe operating within a parking structure is based on both analysis of thedata acquired from the GNSS and analysis of heading changecharacteristics of vehicular movement. In an implementation, thelikelihood that the vehicle is operating within a parking structure asdetermined by the analysis of the data acquired from the GNSS and thelikelihood that the vehicle is operating within a parking structure asdetermined by the analysis of the heading change characteristics of thevehicular movement. Analyzing heading change characteristics may involvecomparing a heading change accumulation calculated at a first time witha heading change accumulation calculated at a second time. Calculatingthe heading change accumulation at various point in time may involvereceiving data from the vehicle sensors 139 and evaluating equationsaccording to values contained within the data received form the vehiclesensors 139. In an implementation, quantitative values indicative of thelikelihood that the vehicle is or is about to be operating within aparking structure may be provided based on an analysis of data acquiredfrom the GNSS chipset/component 132 and based on an analysis of theheading change characteristics of the vehicular movement.

At step 210, a notification indicating that the vehicle is or is aboutto be operating in a parking structure is received by the dead reckoningengine 127 of the telematics unit 114 of the vehicle 102. Vehiclelocation data received by the dead reckoning engine 127 may be providedto the dead reckoning engine 127 by a server 144 at the call center 108of the TSP, by a component of the electronic processing device 128, orby another component of the telematics unit 114 or of the vehiclehardware.

At step 220, the dead reckoning engine 127 activates a parking structureDR mode. The parking garage mode of the dead reckoning engine 127 may bea set of computer executable instructions stored at a computer readablemedium. For example, the computer executable instructions may be storedat the one or more types of electronic memory 110.

At step 230, an estimated horizontal position error (EHPE) of theposition of the vehicle 102 is calculated according to the parkinggarage mode of the dead reckoning engine. Determining the EHPE of thevehicle according to the parking garage mode of the DR engine mayinvolve selecting an equation to use for calculating the EHPE of thevehicle and evaluating the selected equation. Selecting the equation touse for calculating the EHPE of the vehicle may involve specifying anEHPE calculation factor relation, an EHPE calculation factor deltarelation, an offset detecting threshold, an EHPE calculation limitingthreshold, and an accumulated heading change consideration threshold. Avalue for the EHPE calculation factor may be calculated using the EHPEcalculation factor delta relation, the offset detecting threshold, theEHPE calculation factor limiting threshold, and the accumulated headingchange consideration threshold. The EHPE calculation factor deltarelation can specify that the EHPE calculation factor delta is equal toa first value if the accumulated heading change is less than theaccumulated heading change consideration threshold and equal to arelation accounting for the accumulated heading change if theaccumulated heading change is greater than the accumulated headingchange consideration threshold.

In one implementation, at step 230 the EHPE of the position of thevehicle at time k is evaluated to he EHPE(k)=EHPE(k−1)+hE(k)·Δd(k) ifC_(EHPE)(N−1)≦1 and determined to be

${{EHPE}(k)} = \frac{{{EHPE}\left( {k - 1} \right)} + {{{{hE}(k)} \cdot \Delta}\; {d(k)}}}{C_{EHPE}\left( {N - 1} \right)}$

if C_(EHPE)(N−1)<1. hE(k) is the EHE of the vehicle at time k inradians, Δd(k) is the distance traveled from time k−1 to time k, andC_(EHPE)(N−1) is a factor used to calculate EHPE where (N−1)·L≦k−j<NL.C_(EHPE)(N)=C_(EHPE)(N+1)+ΔC_(EHPE)(N) when k−j=NL, C_(EHPE)(0)=0,C_(EHPE)(N)=T₂ if

${{C_{EHPE}(N)} > T_{2}},{{\Delta \; {C_{EHPE}(N)}} = {{0\mspace{14mu} {if}\mspace{14mu} \frac{S_{hd}(k)}{360}} < T_{3}}},{{\Delta \; {C_{EHPE}(N)}} = {{\frac{S_{hd}(k)}{360}\mspace{14mu} {if}\mspace{14mu} \frac{S_{hd}(k)}{360}} \geq T_{3}}},$

S_(hd)(k)=s_(hd)(k−1)+|ΔHd1(k)| when k=j+1, j+2, . . . S_(hd)(j)=0,ΔHd(k)=|Hd(k)−Hd(k−1)|, ΔHd1(k)=|ΔHd(k)−360| if ΔHd(k)>T₃, andΔHd1(k)=ΔHd(k) if ΔHd(k)≧T₁ where Hd(k) is the vehicular heading at timek. T₁ is a threshold used to detect if there is a 360 degrees offsetbetween two adjacent heading values, T₂ is a threshold value to limitthe maximum value of C_(EHPE)(N), and T₃ is a threshold used todetermine if the accumulated heading change is considered in the EHPEcalculation factor. The threshold values for T₁, T₂, and for T₃ may beselected by a variety of methods. In some implementations, the thresholdvalues for T₁, T₂, and for T₃ may be selected to be the same for allparking garage environments. In some implementations, threshold valuesfor T₁, T₂, and for T₃ may be selected uniquely for each parkingstructure identified by the TSP or by another entity that cataloguesinformation pertaining to parking garages. If threshold values for T₁,T₂, and for T₃ are uniquely selected for each parking structure, userfeedback may be utilized to refine the threshold values unique to eachstructure.

FIG. 3 is a flow chart summarizing an example process executed by atelematics service provider for determining whether a vehicle iscurrently operating in a parking structure. At step 300, data acquiredfrom the GNSS chipset/component 132 is analyzed to determine whether ornot the vehicle is operating within a parking structure or is about tobe operating within a parking structure. Analyzing, data acquired fromthe GNSS chipset/component 132 may involve determining the location ofthe vehicle as indicated by the GNSS chipset/component 132 anddetermining whether such location indicated by the GNSSchipset/component 132 corresponds to the location of a parking garage.For example, the location of the vehicle provided by the GNSSchipset/component 132 may be cross-referenced with a list of graphicalareas corresponding to parking garages. The cross-referencing may beperformed by the telematics unit 114 of the vehicle 102, by othervehicle hardware components, by one of the servers 144 of the callcenter 108 of the TSP, or by other hardware elements of the TSP. If itis determined that the vehicle is operating in or near a parkingstructure at step 300, the process proceeds to step 310. Alternatively,if it is determined that the vehicle 102 is not operating in or near aparking structure, the process returns to step 300.

At step 310, a loop counter is set to zero. The loop counter enablesensuing step 320 to be executed multiple times within a loop in order toallow the vehicle time to enter the parking garage in the event that thevehicle is merely operating near the parking garage when the initialdetermination is made at step 300. At step 320, data pertaining toheading change characteristics of vehicular movement is analayzed todetermine whether the vehicle is operating within a parking structure.Analyzing heading change characteristics of vehicular movement at step310 involves determining the value of S_hd(k+L)−S_hd(k), whereinS_(hd)(k) is the heading change accumulation at time k, and S_hd(k+L) isthe heading change accumulation at time k+L. If (k+L)−S_hd(k)>180°, itis determined that the vehicle is operating in a parking garageenvironment, and the process proceeds to step 330 where the deadreckoning engine 127 of the telematics unit 114 of the vehicle 102 isset to a parking garage mode. Thereafter, the process proceeds to step360 where the process ends.

Alternatively, if (k+L)−S_hd(k)≦180°, the process proceeds to step 340where the loop counter is increased by one. At step 350, the processcompares the value of the loop counter to a threshold value. If the loopcounter is less than the threshold value, the process returns to step320. However, if the loop counter is greater than or equal to thethreshold value, the process returns to step 300.

FIG. 4 is a graphical representation depicting the EHPE as determined bya variety of techniques. FIG. 4 depicts the EHPE determined by threedifferent techniques during a test drive of a vehicle within a parkingstructure. The test drive of the vehicle involved the vehicle beingdriven into the garage from an uncovered environment and driven from thefirst floor of the garage to the roof of the garage. On the roof, thevehicle was again in an uncovered environment. Thereafter, the vehiclewas driven from the roof back to the first floor of the garage, and thenout of the garage and back into an uncovered environment. In calculatingthe EHPE with the Parking Garage DR Mode Method, which is set forth inthe description of step 230 of FIG. 2, threshold values of T₁, T₂, andT₃ were chosen to be 200 degrees, 4, and 0.6, respectively. The othertwo methods used to determine EHPE depicted in the graph determine EHPEby multiplying the estimated heading error (EHE) of the vehicle at timek by the distance traveled during a time interval beginning from aprevious point in time at which the vehicle's EHPE was calculated (EHEMethod), and by averaging the EHPE determined by the EHE Method and theEHPE determined by calculating the EHPE with the prediction covariancematrix of the Kalmar filter (Averaging Method).

It will be appreciated by those of skill in the art that the executionof the various machine-implemented processes and steps described hereinmay occur via the computerized execution of computer-executablerecommendations stored on a tangible computer-readable medium, e.g.,RAM, ROM, PROM, volatile, nonvolatile, or other electronic memorymechanism. Thus, for example, the operations performed by the telematicsunit 114 may be carried out according to stored recommendations orapplications installed on the telematics unit 114, and operationperformed at the call center may be carried out according to storedrecommendations or applications installed at the call center.

It is thus contemplated that other implementations of the invention maydiffer in detail from foregoing examples. As such, all references to theinvention are intended to reference the particular example of theinvention being discussed at that point in the description and are notintended to imply any limitation as to the scope of the invention moregenerally. All language of distinction and disparagement with respect tocertain features is intended to indicate a lack of preference for thosefeatures, but not to exclude such from the scope of the inventionentirely unless otherwise indicated.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to”) unless otherwise noted. Recitation of ranges of valuesherein are merely intended to serve as a shorthand method of referringindividually to each separate value falling within the range, unlessotherwise indicated herein, and each separate value is incorporated intothe specification as if it were individually recited herein. All methodsdescribed herein can be performed in any suitable order unless otherwiseindicated herein or otherwise clearly contradicted by context. The useof any and all examples, or exemplary language (e.g., “such as”)provided herein, is intended merely to better illuminate the inventionand does not pose a limitation on the scope of the invention unlessotherwise claimed. No language in the specification should be construedas indicating any non-claimed element as essential to the practice ofthe invention.

Accordingly, this invention includes all modifications and equivalentsof the subject matter recited in the claims appended hereto as permittedby applicable law. Moreover, any combination of the above-describedelements in all possible variations thereof is encompassed by theinvention unless otherwise indicated herein or otherwise clearlycontradicted by context.

1. A method, implemented at a telematics unit of a vehicle, forcalculating the estimated horizontal position error (EHPE) of a positionof a vehicle provided by a dead reckoning (DR) engine, the methodcomprising: determining that the vehicle is operating within a parkinggarage, wherein determining that the vehicle is operating within aparking garage triggers the use of a parking garage mode by a DR engineof the telematics unit; and determining the EHPE of the vehicleaccording to the parking garage mode of the DR engine.
 2. The method ofclaim 1, wherein determining that the vehicle is operating within aparking garage comprises analyzing data received from a GNSS.
 3. Themethod of claim 1, wherein determining that the vehicle is operatingwithin a parking garage comprises analyzing heading changecharacteristics of vehicular movement.
 4. The method of claim 3, whereinanalyzing heading change characteristics comprises comparing a headingchange accumulation calculated at a first time with a heading changeaccumulation calculated at a second time.
 5. The method of claim 3wherein analyzing heading change characteristics of vehicular movementcomprises: determining that S_(hd)(k+L)−S_(hd)(k)>180°, whereinS_(hd)(k) is the heading change accumulation at time k, and S_(hd)(k+L)is the heading change accumulation at time k+L.
 6. The method of claim1, wherein determining the EHPE of the vehicle according to the parkinggarage mode of the DR engine comprises multiplying the distance traveledby the estimated heading error (EHE).
 7. The method of claim 1, whereindetermining the EHPE of the vehicle according to the parking garage modeof the DR engine comprises: selecting an equation to use for calculatingthe EHPE of the vehicle; and evaluating the selected equation; whereinselecting the equation to use for calculating the EHPE of the vehiclecomprises: specifying an EHPE calculation factor relation, an EHPEcalculation factor delta relation, an offset detecting threshold, anEHPE calculation limiting threshold, and an accumulated heading changeconsideration threshold; calculating a value for the EHPE calculationfactor using the EHPE calculation factor delta relation, the offsetdetecting threshold, the EHPE calculation factor limiting threshold, andthe accumulated heading change consideration threshold; and selecting anequation to use for calculating the EHPE of the vehicle based on thecalculated value of the EHPE calculation factor.
 8. The method of claim7, wherein the EHPE calculation factor delta relation specifies that theEHPE calculation factor delta is equal to a first value if theaccumulated heading change is less than the accumulated heading changeconsideration threshold and equal to a relation accounting for theaccumulated heading change if the accumulated heading change is greaterthan the accumulated heading change consideration threshold.
 9. Themethod of claim 1, wherein determining the EHPE of the vehicle accordingto the parking garage mode of the DR engine comprises: determining theEHPE(k)=EHPE(k−1)+hE(k)·Δd(k) if C_(EHPE)(N−1)≦1; and determining that${{EHPE}(k)} = \frac{{{EHPE}\left( {k - 1} \right)} + {{{{hE}(k)} \cdot \Delta}\; {d(k)}}}{C_{EHPE}\left( {N - 1} \right)}$if C_(EHPE)(N−1)>1; wherein EHPE(k) is the EHPE at time k, hE(k) is theEHE of the vehicle at time k in radians, Δd(k) is the distance traveledfrom time k−1 to time k, C_(EHPE)(n−1) is a factor used to calculateEHPE, and (N−1)·L≦k−j<NL, and whereinC_(EHPE)(N)=C_(EHPE)(N+1)+ΔC_(EHPE)(N) when k−j=NL, C_(EHPE)(0)=0, N isa positive integer, C_(EHPE(N)=T) ₂ if C_(EHPE)(N)>T₂, ΔC_(EHPE)(N)=0if${\frac{S_{hd}(k)}{360} < T_{3}},{{\Delta \; {C_{EHPE}(N)}} = {{\frac{S_{hd}(k)}{360}\mspace{14mu} {if}\mspace{14mu} \frac{S_{hd}(k)}{360}} \geq T_{3}}},$S_(hd)(k)=s_(hd)(k−1)+|ΔHd(k)| when k=j+1, j+2, . . . , S_(hd)(j)=0,ΔHd(k)=|Hd(k)−Hd(k−1)|, ΔHd1(k)=|ΔHd(k)−360| if ΔHd(k)<T₁, andΔHd1(k)=ΔHd(k) if ΔHd(k)≦T₁ where Hd(k) is the vehicular heading at timek; and wherein T₁ is a threshold used to detect if there is a 360degrees offset between two adjacent heading values, T₂ is a thresholdvalue to limit the maximum value of C_(EHPE)(N) and T₃ is a thresholdused to determine if the accumulated heading change is considered in theEHPE calculation factor.
 10. The method of claim 9, wherein T₂ is anyvalue greater than 2 and T₃ is any value greater than 0.5.
 11. Acomputer readable medium having stored thereon a set of computerexecutable instructions for calculating the estimated horizontalposition error (EHPE) of a position of a vehicle provided by a deadreckoning (DR) engine, the set of instructions comprising instructionsfor: determining that the vehicle is operating within a parking garage,wherein determining that the vehicle is operating within a parkinggarage triggers the use of a parking garage mode by a DR engine of thetelematics unit; and determining the EHPE of the vehicle according tothe parking garage mode of the DR engine.
 12. The computer readablemedium of claim 11, wherein determining that the vehicle is operatingwithin a parking garage comprises analyzing data received from a GNSS.13. The computer readable medium of claim 11, wherein determining thathe vehicle is operating within a parking garage comprises analyzingheading change characteristics of vehicular movement.
 14. The computerreadable medium of claim 13, wherein analyzing heading changecharacteristics of vehicular movement comprises: determining thatS_(hd)(k−L)−S_(hd)(k)>180°, wherein S_(hd)(k) is the heading changeaccumulation at time k, and S_(hd)(k+L) is the heading changeaccumulation at time k+L.
 15. The computer readable medium of claim 11,wherein determining, the EHPE of the vehicle according to the parkinggarage mode of the DR engine comprises multiplying the distance traveledby the estimated heading error (EHE).
 16. The computer readable mediumof claim 15, wherein determining the EHPE of the vehicle according tothe parking garage mode of the DR engine comprises: determining thatEHPE(k)=EHPE(k−1)+hE(k)·Δd(k) if C_(EHPE)(N−1)≦1; and determining that${{EHPE}(k)} = \frac{{{EHPE}\left( {k - 1} \right)} + {{{{hE}(k)} \cdot \Delta}\; {d(k)}}}{C_{EHPE}\left( {N - 1} \right)}$if C_(EHPE)(N−1)>1; wherein EHPE(k) is the EHPE at time k, hE(k) is theEHE of the vehicle at time k in radians, Δd(k) is the distance traveledfrom time k−1 to time k, C_(EHPE)(N−1) is a factor used to calculateEHPE, and (N−1)·L≦k−j<NL, and whereinC_(EHPE)(N)=C_(EHPE)(N+1)+ΔC_(V)(N) when k−j=NL, C_(EHPE)(0)=0, N is apositive integer, C_(EHPE)(N)=T₂ if C_(V)(N)>T₂,${{\Delta \; {C_{EHPE}(N)}} = {{0\mspace{14mu} {if}\mspace{14mu} \frac{S_{hd}(k)}{360}} < T_{3}}},{{\Delta \; {C_{EHPE}(N)}} = {{\frac{S_{hd}(k)}{360}\mspace{14mu} {if}\mspace{14mu} \frac{S_{hd}(k)}{360}} \geq T_{3}}},{{S_{hd}(k)} = {{S_{hd}\left( {k - 1} \right)} + {{\Delta \; {{Hd}(k)}}}}}$when k=j+1, j+2, . . . , S_(hd)(j)=0, ΔHd(k)=|Hd(k)−Hd(k−1)|,ΔHd1(k)=|ΔHd(k)−360| if ΔHd(k)<T₁, and ΔHd1(k)=ΔHd(k) if ΔHd(k)≦T₁ whereHd(k) is the vehicular heading at time k; and wherein T₁ is a thresholdused to detect if there is a 360 degrees offset between two adjacentheading values, T₂ is a threshold value to limit the maximum value ofC_(EHPE)(N) and T₃ is a threshold used to determine if the accumulatedheading change is considered in the EHPE calculation factor.
 17. Thecomputer readable medium of claim 16, wherein T₂ is any value greaterthan 2 and T₃ is any value greater than 0.5.
 18. A telematics unitconfigured to receive GNSS signals and to determine the position of avehicle through dead reckoning (DR) techniques when it is unable toreceive GNSS signals, the telematics unit comprising: a processorconfigured to determine that the vehicle is operating within a parkinggarage and further configured to execute a parking garage DR mode upondetermining that the vehicle is operating within the parking garagewherein the parking garage DR mode determines an estimated horizontalposition error (EHPE) of the position of the vehicle.
 19. The telematicsunit of claim 18, wherein determining that the vehicle is operatingwithin a parking garage comprises analyzing data received from a GNSS.20. The telematics unit of claim 18, wherein determining that thevehicle is operating within a parking garage comprises analyzing headingchange characteristics of vehicular movement.